class_docstr: This class implements the task-specific Lingvo ASR model of Qin et al. (2019).
  
  The estimator uses a pre-trained model provided by Qin et al., which is trained using the Lingvo library and the
  LibriSpeech dataset.
  
  | Paper link: http://proceedings.mlr.press/v97/qin19a.html, https://arxiv.org/abs/1902.08295
  
  .. warning:: In order to calculate loss gradients, this estimator requires a user-patched Lingvo module. A patched
               source file for the `lingvo.tasks.asr.decoder` module will be automatically applied. The original
               source file can be found in `<PYTHON_SITE_PACKAGES>/lingvo/tasks/asr/decoder.py` and will be patched as
               outlined in the following commit diff:
               https://github.com/yaq007/lingvo/commit/414e035b2c60372de732c9d67db14d1003be6dd6
  
  The patched `decoder_patched.py` can be found in `ART_DATA_PATH/lingvo/asr`.
  
  Note: Run `python -m site` to obtain a list of possible candidates where to find the `<PYTHON_SITE_PACKAGES` folder.
docstr: Define loss gradients computation operation for a batch of padded inputs.
docstr_tok: ["Define","loss","gradients","computation","operation","for","a","batch","of","padded","inputs","."]
code: def _loss_gradient(
      self, x: "Tensor", y: "Tensor", mask: "Tensor"
  ) -> "Tensor":
      """Define loss gradients computation operation for a batch of padded inputs."""
      import tensorflow.compat.v1 as tf1
  
      # create decoder inputs
      decoder_inputs = self._create_decoder_input(x, y, mask)
  
      # call decoder
      if self._metrics is None:
          with self._cluster, tf1.device(self._cluster.GetPlacer()):  # type: ignore
              self._metrics = self._task.FPropDefaultTheta(decoder_inputs)  # type: ignore
  
      # compute loss gradient
      loss = tf1.get_collection("per_loss")[0]
      loss_gradient = tf1.gradients(loss, [x])[0]
      return loss_gradient
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import logging
  import os
  import sys
  from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple, Union
  import numpy
  from art import config
  from art.estimators.speech_recognition.speech_recognizer import SpeechRecognizerMixin
  from art.estimators.tensorflow import TensorFlowV2Estimator
  from art.utils import get_file, make_directory
label_desc: Use image node_id 11 for calling the TensorFlowLingvoASR obj's underlying member method code with example usage: obj._loss_gradient(x, y, mask) and returns: loss_gradient